It gave me a disclaimer in the email "You can't use the gift card balance to purchase other gift cards". But it worked anyways, so whatever. I bought a digital PS4 store card with it.
My family owns all the big switch titles already, but lots of franchises for PS4 I haven't tried. (Witcher, Spyro, Monster Hunter, Uncharted, etc). All of them are on sale, and it helps because I misplaced a gift card I received for christmas.